[ncl-talk] stat_dispersion and standard deviation
jbuzan
jbuzan at purdue.edu
Fri Apr 24 14:51:29 MDT 2015
Thanks Dennis!
-Jonathan
> On Apr 24, 2015, at 4:50 PM, Dennis Shea <shea at ucar.edu> wrote:
>
> ====
> 6.3.0
>
> http://www.ncl.ucar.edu/current_release.shtml <http://www.ncl.ucar.edu/current_release.shtml>
> Under 'Bugs Fixed'
>
>
> stat_dispersion <http://www.ncl.ucar.edu/Document/Functions/Contributed/stat_dispersion.shtml> - The second returned element returned was the sample variance and not the sample standard deviation as is documented. In 6.3.0, the sample standard deviation will be returned.
>
> =====
>
> %> ncl -V
> 6.3.0
>
> a = (/-20.46505, -4.795454, -1.454606,-2.677286, -1.868608, -0.4972475, 1.18715, -1.657706, -3.428875, -2.766053, -1.689298, -0.3371645, -0.640966, -0.7326741/)
>
> opt = True
> opt at PrintStat = True
> stata = stat_dispersion(a, opt )
>
>
> Copyright (C) 1995-2015 - All Rights Reserved
> University Corporation for Atmospheric Research
> NCAR Command Language Version 6.3.0 <====================
> The use of this software is governed by a License Agreement.
> See http://www.ncl.ucar.edu/ <http://www.ncl.ucar.edu/> for more details.
> (0)
> (0) ===> Robust Dispersion Statistics <===
> (0) [0] Mean=-2.98742
> (0) [1] StdDev=5.24311 <=====
> (0) [2] Min=-20.465
> (0) [3] LowDec=-20.465
> [SNIP]
>
>
>
> On Fri, Apr 24, 2015 at 2:25 PM, jbuzan <jbuzan at purdue.edu <mailto:jbuzan at purdue.edu>> wrote:
> I don’t know if this has been fixed in 6.3.0, but there was a change in stat_dispersion and the standard deviation is no longer calculated. it is the variance.
>
> you can change:
> $NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl
> (I renamed the file)
>
> and commented out:
> ; statx(1) = moment(1) ; std. deviation
>
> and replaced with:
> statx(1) = stddev(x) ; std. deviation
>
>
> -Jonathan
>
>
>
>> On Apr 24, 2015, at 4:20 PM, Rainer Luptowitz <rlupt001 at ucr.edu <mailto:rlupt001 at ucr.edu>> wrote:
>>
>> Hi ncl-talk,
>>
>> Is the standard deviation computed in the "stats_dispersion" function actually a variance?
>>
>> I test this and it appears to be variance instead of stats_dispersion as seen in with sample "a" below.
>>
>>
>> Variable: a
>> Type: float
>> Total Size: 56 bytes
>> 14 values
>> Number of Dimensions: 1
>> Dimensions and sizes: [ncl_join | 14] ; I had joined 8 files trends with "addfiles" function
>> Coordinates:
>> Number Of Attributes: 0
>> (0) -20.46505
>> (1) -4.795454
>> (2) -1.454606
>> (3) -2.677286
>> (4) -1.868608
>> (5) -0.4972475
>> (6) 1.18715
>> (7) -1.657706
>> (8) -3.428875
>> (9) -2.766053
>> (10) -1.689298
>> (11) -0.3371645
>> (12) -0.640966
>> (13) -0.7326741
>>
>> ; ncl code compare variance to standard deviation
>>
>> ; the above data was placed into an array named "a"
>> a = (/-20.46505, -4.795454, -1.454606,-2.677286, -1.868608, -0.4972475, 1.18715, -1.657706, -3.428875, -2.766053, -1.689298, -0.3371645, -0.640966, -0.7326741/)
>>
>>
>> ; Input
>> Var_a = variance(a) ; calc variance
>> print(Var_a)
>> StdDev_a = stddev(a) ; calc standard deviation
>> print(StdDev_a)
>> opt = True
>> opt at PrintStat = True
>> Stats_a = stat_dispersion(a,opt)
>>
>>
>> ; Output
>> ; from individually calculating Variance
>> Variable: Var_a
>> Type: float
>> Total Size: 4 bytes
>> 1 values
>> Number of Dimensions: 1
>> Dimensions and sizes: [1]
>> Coordinates:
>> (0) 27.49021
>>
>> ; from individually calculating Standard Deviation
>> Variable: StdDev_a
>> Type: float
>> Total Size: 4 bytes
>> 1 values
>> Number of Dimensions: 1
>> Dimensions and sizes: [1]
>> Coordinates:
>> (0) 5.243111
>>
>> ; from Stats_Dispersion function.
>> (0)
>> (0) ===> Robust Dispersion Statistics <===
>> (0) [0] Mean=-2.98742
>> (0) [1] StdDev=27.4902 ; this appears to be variance since
>> (0) [2] Min=-20.4651
>> (0) [3] LowDec=-20.4651
>> (0) [4] LowOct=-20.4651
>> (0) [5] LowSex=-4.79545
>> (0) [6] LowQuartile=-3.42888
>> (0) [7] LowTri=-2.76605
>> (0) [8] Median=-1.6735
>> (0) [9] HighTri=-1.45461
>> (0) [10] HighQuartile=-0.732674
>> (0) [11] HighSex=-0.640966
>> (0) [12] HighOct=-0.497248
>> (0) [13] HighDec=-0.497248
>> (0) [14] Max=1.18715
>> (0) [15] Range=21.6522
>> (0) [16] Dispersion=0.787633
>> (0) [17] RMS Anomaly=5.05239
>> (0) [18] # Total=14
>> (0) [19] # Used=14
>> (0) [20] # Missing=0
>> (0) [21] % Missing=0
>> (0) [22] Lower 0.1%=9.96921e+36
>> (0) [23] Lower 1.0%=9.96921e+36
>> (0) [24] Lower 5.0%=9.96921e+36
>> (0) [25] Upper 5.0%=9.96921e+36
>> (0) [26] Upper 1.0%=9.96921e+36
>> (0) [27] Upper 0.1%=9.96921e+36
>> (0) [28] Skewness=-2.57898
>> (0) [29] Kurtosis=5.86411
>>
>>
>> What do you think?
>>
>> Thank you for time and assistance,
>>
>> Rainer Luptowitz
>> Grad Student
>> Dept Earth Sciences
>> UC Riverside
>> rlupt001 at ucr.edu <mailto:rlupt001 at ucr.edu>
>>
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